Metal spray gun



Patented F eb. 8,

UNi'rEo STATES PATENT oI-ric` METAL SPRAY GUN Arthur P. Shepard, ForestHills, N. Y., assignor to Metaliizing Engineering` Company, Inc., LongIsland City, N. Y., a corporation of New Jersey Application July 31,1940, Serial No. 348,633

(Cl. Sil-12.2)

17 Claims.

This inventionY relates to improvements in metal spray guns.

Metal spray guns of the wire feeding .gas blest type are devices inwhich a. metal rod or wire is continuously fed into a melting zone inwhich the metal is melted, being thereafter finely divided and expelledfrom the gun in sub-divided form by a. blast of air or other ges. Amixture of combustible and combustion supporting gases,

, tip, provided with e. wire feeding orice end s.

multiple number oi burner iets, substentially surrounding the exis ofsaid orice, end en sir cop, extending with e portion of its innersurface, edjacent the air oep tip, toin advance of seid ori- `iice,preferably in substentislly converging reletion to said exis, anddefining with a. backwerdly extending portion of its inner surface nudwith seid burner tip e gas blast passage. It is to such nozzleconstruction that the invention primarily relates.

The hitherto used metal spray guns of the wire feeding ges blast ere ofrelatively low spi-eying speed end emciency end ere subject to thedanger of bog, i. e., 'the ignition of the combustible ges mixtureinside the ges jets or the gas passages.

I have devised an improved nozzle construction for s. metal spray gun ofthe wire feeding gas blest type permitting a more emcient and higherspeed spraying of metal with a materially reduced tendency to backfire,then wos hitherto possible with conventional devices.

The invention vwill be more fully understood from the followingdescription read in conjunction with the drawing illustrating apreferred embodiment of the structure in accordance with the inventionin whichl Fig. l is e vertical section through a preferred embodiment ofs nozzle construction in sccord ance with my invention;

Fig. 2 is on end view of the construction illustrated in Fig. 1 in theplene indicated b II-II;

Fig. 3 is e sectional view of the burner tip pon` tion of theconstruction illustrated in Fig. 1 in the plane indicated by III-III,and

Fig. 4 represents e sectional view of .the burner tip and air capportion of the construction illustrated in Fig. 1 on the plane indicatedby IV-IV.

Referring to the drawing, l represents the inner nozzle or burner tip; 2represents the air capwhich is adjustebly screwed by e. thread Si into ehousing t. The housing il is secured to the gun head of which only partis shown in the drawing. The inner nozzle or burner tip i is Isented onthe iiat seat t of heed 5 end is held there securely by nut l. Air cap 2has two slots cut in its rim at i es illustrated in Figs. l and 4. Locknut t is provided for securing oir csp 2 in eny desired position. A portit leeds from a mixing chamber for combustible end combustionsupportinggases (not shown), to circuler channel ii cut in the fiat seat t. Innernozzle or burner tip i is provided with a multiple number of gespossoges i2. Communicating with these gas passages ere burner jets itand it. These burner jets it and ld ore alternately spaced es indicatedin Fig. 3. Burner jets it extend to the tip of the inner nozzle, whileburner jets it communicate with enlarged jet portions l5. Enlarged ietportions it extend to the discharge end of the inner nozzle or burnertip es indicated in Fig. i. Mounted et the discharge end of lnner nozzleor burner tip i is e. bushing it which l is set beck slightly from theburner jet openings.

Burner tip i is constructed with o substentislly cylindrical surface il'which extends into end is concentric with the cylindrical surface orbore l@ of the eir csp i. Part of the inner surface oi' sir csp 2 hes aconical surface it with o comparstively shallow angle of slope relativethe air' csp axis or the axis of the wire feeding criiice. This rstconical surface i9 adioins s. second conical surface 2t, edit the aircsp tip, with a comparatively steeper angle of slope relative such ems.The surface at the juncture of the two conical sections i9 end 2d isprefersbly curved slightly es et il. The rod-like shape of metei i2extends through wire'ieeding orice formedby guide bushing it in theinner nozzle or burner tip i.' Y

In the practical operstion of the improved gun nozzle structure inaccordance with my invention, e mixture of combustible and combustionsupporting gases enters through gas passage it and thence throughchannel Il to ses pesssges i2 in the inner nozzle or burner tip l. Gaspessages I2, alternately connected with burner jets -tained bycounterborlng I3 and I4 permit the combustible mixture of gases to flowto the discharge end of inner nozzle or burner tip I. The gas enteringburner jets I3 passes directly to the discharge end of the burner tipwhereas the gas entering burner jets I4 flows first through enlarged jetportions I5 before passing to the discharge end of the burner tip I.Burner jets I3 are larger in crosssectional area than burner jets I4,whereas enlarged burner jet portions I5, preferably obor countersinkingburner jets I4, are of larger cross-sectional area than jets I4. In manycases it is of advantage and preferred to construct enlarged jetportions I5 also of larger cross-sectional area than burner jets I3.When resorting such construction the combustible gas mixture enteringgas passages I3 from channel Il, under substantially the same pressure,permits a greater volume of gas to flow through the wider jets I3 thanflows through the smaller jets I4. This particular distribution of thecombustible gases substantially eliminates the shrill undesirablewhistle which sometimes occures when the same .volume of gas ispermitted to discharge from each of the burner jets which is especiallynoticeable when using propane as the combustible gas component of themixture. In most instances a few thousandth.. of an inch differencebetween the cross-sectional areas of burner jets I3 and I4 will give thedesired result. The names issuing from the enlarged jet portions, suchas jet portions I5, are shorter than the flames issuing from thedischarge end of the non-enlarged jets, such as jets I3. When enlargedjet portions are substantially evenly distributed among the burner .ietssurrounding the axis of the wire feeding orifice and particularly whensuch enlarged burner jet portions alternate with non-enlarged burner jetopenings, as illustrated in the preferred embodiment of the inventionshown in the drawing, a substantially ribbed-like flame is produced withthe hot tip of the flames, issuing from burner jets i3, projectingfarther than the hot tips of the flames, issuing from the burner jetsi5, inwhich manner the melting zone is considerably elongated. Thislonger heating zone permits a more rapid melting of the metal and evenof relatively high melting point metals so that the metal wire 4or rod22 passing through the Wire feeding orince as defined by the bushing IBmay be fed more rapidly through the nozzle and permits a more eillcientand speedier spraying operation. As shown in the drawing, the wirefeeding orice through the bushing Il is set back slightly relative thedischarge ends or openings of burner iets I3 and I4. vSuch constructiongreatly reduces the hazards of backnring and thus permits the use of agreater combustible gas flow with a resultant increase in spraying speedand eilliency. When used in conjunction with other structural elementsof the improvedconstruction in accordance with the invention, tending toenhance spraying speed and emciency or to reduce backre hazards, it willstill further enhance these advantages.

Air or other blasting gas enters chamber 26 under pressure from an inletduct (not shown). This blasting gas passes through a substantiallyannular pressure reduction orifice 23, .substantially donned' by thecylindrical surface I8, formed on the backwardly extending portion ofthe inner surface of the 'air cap 2, and the cylindrical surface I1,formed by a part of the backwardly extending surface of the inner nozzleor burner tip I. After passing the pressure reduction orifice 23 theblasting gas enters chamber 24 and flows thence through the spacebetween the sloped inner surface I9 of air cap 2 and the surface of theconical end of the inner nozzle or burner tip I, defining annularorifice 25, and out through the discharge end of the air cap 2. Theinner surface of the air cap 2, adjacent the discharge end thereof, hasan average angle of slope, with respect to the axis of the wire feedingorifice, greater than the average angle of slope, with respect to suchaxis, of its adjoining inner surface portion IB. As illustrated, bothsurface portions I9 and 20 each form a conical surface, the conicalsurface 20 having a greater average angle of slope, with respect to theaxis of the wire feeding orifice, than has the conical surface I9. Theblasting gas, passing with relatively high velocity through annularorifice 25, is deflected at a relatively small angle to the axis of thewire feeding orifice by the lesser sloped surface I9 of air cap 2. Thisrelatiyely shallow angle of surface I9 permits the blasting gas to passoutside of the envelope of flame in advance of the inner nozzle orburner tip I before being deected by the steeper angled inner air capsurface 20. The blasting gas will thus converge at the most desirablesteep angle at a point sufnciently in advance of the flame envelopevtosubstantially avoid the building up of a detrimental back pressure atthe discharge end of the inner nozzle or Iburner tip I. The rapid andrelatively steep angled convergence of the blasting gas at the moltentip of the metal wire or rod produces a very fine and complete break-upor atomization of the metal and blasts the same forward in a strong nespray.. In this manner a more eflicient and speedier spraying operationis realized and, when using such construction in conjunction with theburner jet construction in accordance with the invention. the increasein spraying efficiency and speed, already greatly improved by such jetconstruction, is still further enhanced by this inner surface doubleslope improvement in the air cap. The material reduction in backpressure at the discharge end of the inner nozzle or burner tip I,obtained when' using the inner surface double slope construction, inaccordance with the invention, considerably lessens the tendency tobackfire. This beneficial effect is still further enhanced by utilizingthis construction in conjunction with other structural features of myimproved nozzle construction which possess such backfire hazard reducingeffect.

W'hen using the inner air cap surface double slope construction, inaccordance with the invention, I have foundy it of advantage to utilizean average angle of slope, with respect to the axis of the wire feedingorice, of the surface portion adjacent the air cap tip, of approximately5 to 15 degrees and preferably of 10 to 11 degrees and an average angleof slope, relative such axis, of the gas blast passage delimitingportion of its inner surface, of approximately 3 to l2 degrees andpreferably of 51/2 to 6% degrees.

The provision of an air reduction orice of substantially constantcross-sectional area throughout a given longitudinal adjustment of theair cap permits the adjustment of the air cap 2 with respect to thedischarge end of the burner tip I without materially affecting thequantity of now of the blasting gas and irrespective of whether the aircap is moved towards or away from the burner tip. This construction alsoaids in increasing the spraying emciency and speed and further aids inmaterially reducing the danger of backring as it tends to eliminate thebuilding up of back pressure which would result when moving the air captowards the burner tip in the -absence of the substantially constantcross-sectional area, pressure reduction orifice, in accordance with theinvention.

Air cap 2 is preferably provided adjacent its threaded end 3 as shown inFigs. 1 and 4 with slots 8 to prevent the possibility of accidentallyshutting off the gas blast supply from chamber 26 by screwing the aircap 2 back too far until the back. of its end strikes nut 7. With theprovision of such slots 8 sumcient air will pass through these slotseven if the air cap 2 is screwed back as far as it will go.

The foregoing description is furnished by way of illustration and not oflimitation and'it is, therefore, my intention that the invention belimited only by the appended claims or their equivalents wherein I haveendeavored to claim broadly all inherent novelty.

I claim:

1. In the nozzle construction of a wire feeding metal spray gun of thegas blast type, including a burner tip provided with a wire feedingorifice, a multiple number of burner jets substantially surrounding theaxis of said orifice and means to supply a combustible gas through saidjets, the improvement comprising an air cap having a first inner surfaceportion immediately surnounding said burner tip, defining therewith atleast one gas blast passage, start' at a pOint prior to said orifice andhaving only one other second inner surface portion extending said gasblast passage to in advance of said orifice, and directing gas blast,issuing fromisaid gas blast passage, against the molten tip of the wirefeeding through said orifice, the average angle of slope, with respectto said axis of said second inner surface portion being greater than theaverage angle of slope, with respect to said axis, of said first innersurface portion.

2. The improvement in accordance with claim l in which said first andsecond inner surface portions each defines a conical surface.

3. In the nozzle construction of a Wire feeding metal spray gun of the`gas blast type, including a burner tip provided with a wire feedingorifice, a multiple number of burner jets substantially surrounding theaxis of said orifice and means to supply 'a combustible gas through saidjets, the

improvement comprising an air cap, substantially v longitudinallyadjustable with respect to said burner tip and having a first innersurface portion immediately surrounding said burner tip dening therewithat least one gas blast passage, starting at a point prior to saidorifice and having only one other second inner surface portion extendingsaid gas blast passage to in advance of said orifice, and directing gasblast, issuing from said gas blast passage, against the molten tip ofthe wire feeding through said orifice, the average angle of slope withrespect to said axis of said second inner surface portion being greaterthan the average angle of slope, with respect to said aids, of saidfirst inner surface portion, said burner tip and said air cap havingcooperating backwardly extending surfaces, and, in communica- 'tion withsaid gas blast passage, a blasting gas pressure reduction orifice ofsubstantially constent cross-sectional area throughout a givenlongitudinal adjustment of said air cap, said pressure reduction orificebeing defined by at least part of said backwardly` extending surfaces.

4. The improvement in accordance with claim 3 in which said blasting gaspressure reduction orifice is a substantially 'annular orifice and inwhich said backwardly-extending surfaces form substantially cylindricalsurfaces substantially coaxially aligned with said burner tip.

5. In the nozzle construction of a wire feeding metal spray gun of thegas blast type, including a burner tip provided with a wire feedingorice, a multiple number of burner jets substantially surrounding theaxis of said orifice and means to supply a combustible gas through saidjets, the improvement comprising an air cap, substantiallylongitudinally adjustable with respect to said burner tip and having aflrst inner surface portion immediately lsurrounding said burner tip,defining therewith' at least one gas blast passage, starting at a pointprior to said orifice and having only one other second inner surfaceportion extending said gas blast passage to in advance of said orifice,and directing gasvblast, issuing from said gas blast passage, againstthe molten tip of the Wire feeding through said orifice, said burner tipand said air cap having cooperating backwardly extending surfaces, and,in communication with said gas blast passage, a blasting gas pressurereduction orifice of substantially constant crosssectional areathroughout ag'iven longitudinal adjustment of said air cap, saidpressure reduction orifice being dened byat least part of saidbackwardly extending surfaces. L

6. The improvement in accordance with claim 5 in which said blasting gaspressure reduction. orifice `is a substantially annular orifice and inwhich said backwardly extending surfaces form substantially cylindricalsurfaces substantially co-axially aligned with said burner tip.

'1. In the nozzle construction of a wire feeding metal spray gun of thegas blast type, including a burner tip provided With a wire feedingorifice, a multiple number of burner jets substantially surrounding theaxis of said orifice and means to supply a combustible gas through saidjets, the l improvement comprising an air cap, substantiallylongitudinally adjustable with respect to said burner tip and having afirst inner surface portion immediately surrounding said burner tip,defining therewith at least one gas blast passage, starting at a pointprior to said orifice and lhaving only one other secondA inner surfaceportion extending said gas blast passage to in advance of said orifice,and directing gas blast, issuing from said gas blast passage, againstthe molten tip of the wire feeding through said orifice, the averageangle of slope, with respect to said axis of said second inner surfaceportion being greater than the average angle of slope, with respect tosaid axis,l of said first inner surface portion, and a multiple numberof burner Jets, at least some of which being, at least at their endportions, adjacent the jet openings, of larger cross-sectional area thanthe remaining jets, at least at their end portions, adjacent the jetopenings.

8. The improvement in accordance with claim 7 in which at least some ofsaid burner jets are at their-end portions, adjacent the Jet openings,of larger cross-sectional area than the jet portions, extendingbackwardly therefrom.

9. The improvement in,accordance with claim 7 in which each alternate ofsaid burner jets isl f at its end portion, adjacent the jet opening, of

larger cross-sectional area than its jet portion,

extending backwardly therefrom and of larger cross-sectional area thanthe corresponding jet portions of the other burner jets.

l0. Theimprovement in accordance with claim 'l in which each alternateof said burner jets is at its end portion, adjacent the jet opening, oflarger cross-sectional area than its jet portion extending backwardlytherefrom and in which said backwardly extending jet portion is ofsmaller in advance of said orifice, and directing gas blast, i

- issuing from said gas blast passage, against the molten tip of thewire feeding through said orince, the improvement comprising a multiplenumbei of burner jets, at least some of which being, at least at theirend portions, adjacent the jet openings, of larger cross-sectional areathan the remaining jets, at least at their end portions, adjacent thejet openings.

12. In the nozzle construction of a wire feeding metal spray gun of thegas blast type, including 'a burner tip provided with a wire feedingorifice, a multiple number of burner jets substantially surrounding theaxis of said orifice, means to supply a combustible gas through saidjets and an air cap having a first inner surface portion immediatelysurrounding said burner tip defining therewith at least one gas blastpassage and having a second inner surface portion extending to inadvance of said orifice, and directing gas blast, issuing from said gasblast passage, against the molten tip of the wire feeding through saidorifice, the improvement comprising a multiple number of burner jets, atleast some of which being at their end portions, adjacent the jetopenings, of larger cross-sectional area than the jet portions,extending backwardly` therefrom.

13. In the nozzle construction of a wire feeding metal spray gun of thegas blast type, including a burner tip provided with a wire feedingorifice, a multiple number of -burner jets substantially surrounding theaxis of said orifice, means to supply a combustible gas through saidjets and an air cap having a rst inner surface portion immediatelysurrounding said burner tip, defining therewith at least one gas blastpassage, Startins surrounding the axis of said orice and means to supplya combustible gas through said jets, the improvement comprising anaircap, substantially longitudinally adjustable with respect to said burnertip and having a first inner surface portion immediately surroundingsaid burner tip, defining therewith at least one gas blast passage,starting at a point prior to said orifice and having only one othersecond inner surface portion extending said gas blast passage to vinadvance of said orifice, and directing gas blast, issuing from said gasblast passage, against the molten tip of' the wire feeding through saidorifice, the average angle of slope, with respect to said axis of saidsecond inner surface portion being greater than the average angle ofslope, with respect to said axis, of said first inner surface portion, amultiple number of burner jets, each alternate of which being at its endportionadjacent the jet opening, of larger cross-sectional area than itsjet portion extending backwardly therefrom, said backwardly extendingjet portion being of smaller crosssectional area than the jet portionsof smallest cross-sectional area of the other burner jets, said burnertip and said air cap having cooperating backwardly extending surfaces,and, in communication with said gas blast passage, a substantiallyannular blasting gas pressure reduction orifice of substantiallyconstant cross-sectional area throughout a given longitudinal adjustmentof said air gap, said pressure reduction orifice being defined by atleast part of said backwardly extending surfaces to form substantiallycylindrical surfaces having a substantially common axis with said burnertip. .r

15. In the nozzle construction of a wire feeding metal spray gu'n of thegas blast type, including a burner tip provided with a wire feedingorifice, a multiple number of burner jets substantially surrounding theaxis ofl said orifice and means to supply a combustible gas through saidjets, the

improvement comprising an air cap, substantially longitudinallyadjustable with respect to said burner tip and having a first innersurface portion immediately surrounding said burner tip, deningtherewith at least one gas blast pasv sage, starting at a point prior tosaid orifice and at a point prior to said orifice and having; only oneother second inner surface portion extending said gas blastfpassage toin advance of said orince, and directing gas blast, issuing from saidgas blast passage, against the molten tio of the wire .feeding throughsaid orifice, the improvement comprising a multiple number of burnerjets, each alternate of which being at its end portion, adjacent the jetopening, of larger cross-sectional area than its jet portion extendingbackwardly there.-

' from, said backwardly extending jet portion being of smallercross-sectional area than the jetportions of smallest cross-sectionalarea of the'other burner jets.

14. In the nozzle construction of a wire feeding metal spray gun o! thegas blast type, including a burner tip provided with a wire feedingorifice,

a multiple number of burner jets substantially having only one othersecond inner surface portion extending said gas blast passage to inadvance of said orifice, and directing gas blast, issuing from said gasblast passage, against the molten tip of the wire feeding through saidorifice, the average angle of slope, withl respect to said axis of saidsecond inner surface portion being greater than the average angle ofslope, 'with respect to said axis, of said rst inner surface portion,and a wire feeding orifice set back lative to at least some of theburner jet opengs. Y

16. In the nozzle construction of a wire feeding metal spray gun of thegas blast type. including a burner tip provided with a wire feedingorifice, a multiple number of burner jets substantially surrounding theaxis of said orifice, means tc supply a combustible gas through saidjets and an air cap having a first inner surface portion immediatelysurrounding said burner tip defining therewith at least one gas blastpassage and having a second inner surface portion extending to inadvance of said orifice, and directing gas blast, issuing from said gasblast passage, against the molten tip of the wire feeding through saidorifice, the improvement comprising a wire feeding orice set backrelative to at least some of tho '2,340,903 burner jet openings and theface of the burner 17. In the nozzle construction of a wire feedingmetal spray gun of the gas blast type, including a burner tip providedwith a wire feeding orice, a multiple number of burner jetssubstantially surrounding the axis of said oriiice and means to supply acombustible gas through said jets, the improvement comprising an aircap, substantially longitudinally adjustable with respect to said burnertip and having a rst inner surface por tion immediately surrounding saidburner. tip,

dening therewith at least one gas blast passage, -h

starting at a point prior to said orifice and havmg only one othersecondinner surface portion extending said gas blast passage to inadvance of said orifice, and directing gas blast, issuing from said gasblast passage, against the molten tip of the wire feeding through saidorifice, the average angle of slope, with respect to said axis, of said`second inner surface portion being'greater than the averagev angle ofslope,'with respect to said axis, of said first inner surface portion,said first inner surface portion dening a irst conical surface and saidsecond inner surface portion denn'- ing a second conical surface, amultiple number of burner iets, each alternate of which being at its endportion, adjacent its jet opening, of larger cross-sectional yarea thanits jet portion extendv ing backwardly therefrom, said backwardlyextending jet portion being of smaller cross-sectional area than the jetportions of 'smallest crosssectional area of the otherburner jets, awire feeding orifice set back relative\the burner jet openings andtheface of the burner tip, said burner tip and said air cap havingcooperating backwardly extending surfaces, and, in communication withsaid gas blast passage, a substantially

